红黑树的原理及特点及其在Python中的代码实现

import sys# 创建节点class Node():    def __init__(self, item):        self.item = item        self.parent = None        self.left = None        self.right = None        self.color = 1class RedBlackTree():    def __init__(self):        self.TNULL = Node(0)        self.TNULL.color = 0        self.TNULL.left = None        self.TNULL.right = None        self.root = self.TNULL    # 前序    def pre_order_helper(self, node):        if node != TNULL:            sys.stdout.write(node.item + " ")            self.pre_order_helper(node.left)            self.pre_order_helper(node.right)    # 中序    def in_order_helper(self, node):        if node != TNULL:            self.in_order_helper(node.left)            sys.stdout.write(node.item + " ")            self.in_order_helper(node.right)# 后根    def post_order_helper(self, node):        if node != TNULL:            self.post_order_helper(node.left)            self.post_order_helper(node.right)            sys.stdout.write(node.item + " ")    # 搜索树    def search_tree_helper(self, node, key):        if node == TNULL or key == node.item:            return node        if key